.allout {
  width: 100%;
  height: 100%;
  background: #f5f5f5 url('../../assets/beijingtu.png') no-repeat center / contain;
  background-size: 100%;
}
.btn {
    width: 100px;
    height: 100px;
    position: absolute;
    bottom: 20px;
    left: 50%;
  }
